Technical Field
The present invention relates to a photoconductor, an image forming apparatus including the photoconductor, and a process cartridge including the photoconductor.
Description of the Related Art
In an image forming method using an image forming apparatus, an image is formed by performing, for example, a charging step, an irradiating step, a developing step, and a transfer step. Recently, an organic photoconductor containing an organic material is widely used as a photoconductor of the image forming apparatus because of advantages such as flexibility, thermal stability, and film-forming property.
Recently, there is a need for photoconductors to have greater degrees of durability and stability along with rapid advancement in full-color, high-speed, and high-definition properties of image forming apparatuses. Moreover, improvement in a surface layer such as a protective layer drastically improves the photoconductor in abrasion durability. Meanwhile, there is a need for each layer constituting the photoconductor (e.g., a photosensitive layer, an intermediate layer, and an undercoat layer) to have electric durability, chemical durability, and stability of electric property to fluctuation of usage environment.
An organic material constituting a photoconductor gradually changes in quality through electrostatic load in the typical electrographic process including repetitive charging and charge neutralizing. As a result, the photoconductor is deteriorated in electric property, and cannot retain electric stability when the photoconductor is used for a long term. It is known that deterioration in charging property adversely affects quality in output images, and causes serious problems such as deterioration in image quality, background fog (hereinafter may be referred to as background stain, fog, and black spots), poor uniformity of images during continuous outputs. It is believed that these problems are closely related to the undercoat layer of the photoconductor. Therefore, improvement in the undercoat layer is necessary in order to obtain durability and high stability of the photoconductor.
Generally, an organic photoconductor includes an electroconductive substrate containing, for example, aluminum, an undercoat layer formed on the substrate, and a photosensitive layer formed on the undercoat layer. The undercoat layer is an electroconductive layer mainly containing a binder resin and electroconductive particles such as metal oxide particles. The undercoat layer is usually formed to provide three functions, which are to be improved: “the function of leakage resistance”, which is obtained by covering the surface of the substrate with the undercoat layer; “the function of preventing injection of charges” from the substrate to the photosensitive layer; and “the function of transporting charges” to the substrate, where the charges are generated in the photosensitive layer.